- Crown-of-thorns starfish (Acanthaster planci) eat live coral. They are native to Australia, but outbreaks in recent years have been blamed for destroying up to 40 percent of the Great Barrier Reef.
- Scientists at Queensland University of Technology developed an autonomous underwater robot that can identify crown-of-thorns starfish inject hundreds of the animals with a lethal injection on a single 8-hour mission.
- After ten years in development, the robot completed its first sea trials last week. Scientists hope to turn it loose on the reef in December, and eventually to release an army of the killer robots.
It’s like the plot of a science-fiction film: scientists develop killer robots to take out their targets with lethal injections. Only the targets in this case aren’t government enemies or criminals on the lam, but bizarre marine pests called crown-of-thorns starfish (Acanthaster planci).
These starfish feed on live coral, surrounding their prey with their stomachs and slathering them with digestive enzymes. The starfish can be so voracious that scientists have blamed them for destroying up to 40 percent of the Great Barrier Reef over the last 30 years. Now, scientists are just months away from deploying an autonomous underwater robot armed with hundreds of lethal injections to seek out and kill crown-of-thorns starfish across the world’s largest reef, according to a press release from the University of Queensland.
Crown-of-thorns starfish live across the Indo-Pacific Ocean, and are native to Australia. In small populations they do little harm, and arguably help keep reefs diverse and healthy. But in recent years conservationists have become increasingly concerned about what appear to be outbreaks of the coral-eaters, especially in the Great Barrier Reef.
While scientists continue to debate the cause of these outbreaks, many believe that fertilizer runoff from agriculture has played a major role. The sudden input of high levels of nutrients leads to a boom in phytoplankton, the primary food of crown-of-thorns starfish larvae. More larvae eventually mean more adult crown-of-thorns starfish devouring coral. However, other theories include the loss of the starfish’s predators or recent El Niño oceanic temperature patterns, which are posited to aid the survival of larvae.
The issue has led the Australian government and many environmentalists to declare war on the starfish. Already, human divers are pursuing crown-of-thorns starfish and killing them with single injections of a substance known as thiosulfate-citrate-bile salts-sucrose agar — TCBS, for short. TCBS is a laboratory-refined version of cattle bile and has been proven a rapid killer of crown-of-thorns starfish with 100 percent mortality.
The new robot, armed with hundreds of doses of TCBS, may be able to take the fight to the next level.
“It will never out-compete a human diver in terms of sheer numbers of injections but it will be more persistent,” the robot’s designer, Matthew Dunbabin, a researcher at the Queensland University of Technology, told the Australian Associated Press. “It can go out for long periods of time and in all weather conditions.”
Dunbabin and his team dubbed the killer robot “COTsbot,” short for “crown-of-thorns-bot.” Resembling a small yellow submarine, the robot identifies its target through advanced recognition software based on thousands of images and 3D-models of its targets.
“This system has been trained to recognize [crown-of-thorns starfish] from among a vast range of corals using thousands of still images of the reef and videos taken by…divers,” Dunbabin told the BBC.
And if it is unsure of a particular target, the robot will send a message to home base for clarification. Dunbabin told the Australian AP that he was “99.99% confident in its accuracy.”
The designers believe each robot will be able to cruise the reefs for eight-hour trips, delivering as many as 200 lethal doses per voyage. After ten years in development, it completed its first sea trials last week, testing out its mechanical and navigation systems. Later this month Dunbabin’s team will take it to the Great Barrier Reef to test its mettle against living crown-of-thorns starfish. They hope to turn it loose on the reef in December, and eventually to release an army of the killer robots.
In addition to the crown-of-thorns starfish, the Great Barrier Reef faces numerous challenges, including pollution from mining, overfishing, eutrophication from agriculture, wetland destruction, heavy shipping, and port development and subsequent dredging to promote coal exports.
But in coming decades, climate change may overwhelm all of these. Already the reef has faced several coral bleaching outbreaks linked to high ocean temperatures and an increasing number of cyclones, which may also be connected to global warming. Last year, the Great Barrier Reef Outlook Report 2014 by the Australian government found that climate change was the most significant threat to the world’s largest reef.
“[Climate change] is already affecting the reef and is likely to have far-reaching consequences in the decades to come,” the report concluded.
Still, research elsewhere has shown that healthy coral reefs display greater resilience against climate impacts. Conservationists hope that if they can neutralize the threat of crown-of-thorns starfish outbreaks, the reef will have a better chance of surviving the century.
Citations
Great Barrier Reef Marine Park Authority (2014). Great Barrier Reef Outlook Report 2014. Australian Government. Great Barrier Reef Marine Park Authority, Townsville, Queensland, Australia.